The present invention relates to a process for producing chlorophenylhydrazine compounds from phenylhydrazine compounds of which the nitrogen atoms on beta-position are protected. More particularly, the present invention relates to a process by which chlorophenylhydrazine compounds which are useful as starting materials for the production of herbicides, insecticides and photographic couplers are produced in high yields from phenylhydrazine compounds of which the nitrogen atoms on beta-position are protected.
Phenylhydrazine compounds having chlorine atoms on the phenyl nucleus (e.g., 2,4,6-trichlorohydrazine) are used as intermediates for the production of such chemicals as herbicides [e.g., propionyl chloride, (2,4,6-trichlorophenyl)hydrazone and isobutyryl(2,4-dichlorophenylhydrazone)] and pyrazolone-type photographic magenta couplers.
The method heretofore used to manufacture chlorophenyl-hydrazine compounds from phenylhydrazine compounds of which the nitrogen atoms on beta-position are protected is described in, for example, J. Humphries, H. Humble, and R. Evans; J. Chem. Soc., 127, 1304-1307 (1925). That is, a particular phenylhydrazine compound is converted to hydrazone by protecting with aldehyde or ketone, then at least one hydrogen atom on the phenyl nucleus is chlorinated and, subsequently, the chlorinated hydrazone is reduced with an appropriate chemical such as zinc. However, zinc which is typically used as a reducing chemical contains cadmium as an impurity, so the post-treatment of the reaction residue is a great concern not only with respect to environmental aspects but also from an economical viewpoint. A further problem is concerned with the aldehyde or ketone which is used as a protective group for the nitrogen atom on beta-position in the phenylhydrazine compound: after reduction such aldehyde or ketone would be eliminated in the form of a compound where the bond to the nitrogen atom on beta-position has been methylated or methylenated. Since the thus eliminated compounds can no longer be reused as a protective group, the cost of the final product will inevitably increase.